The present invention relates to a charged-particle beam apparatus such as a scanning electron microscope, and to a method and apparatus for inspecting or measuring patterns on a semiconductor substrate or the like based on charged-particle beam imaging.
In recent years, wiring patterns formed on a semiconductor substrate or the like are becoming much smaller in dimensions. Therefore, it is necessary to detect extraneous substances or defects on fine patterns or measure the dimensions of fine patterns formed on a subject of inspection or measurement (will be termed xe2x80x9csamplexe2x80x9d hereinafter), e.g., a semiconductor substrate, based on the projection of a charged-particle beam, e.g., an electron beam, to the sample, the detection of charged particles, e.g., secondary electrons or reflected electrons, from the sample, and the processing of a signal derived from the detected charged-particles.
A sample of semiconductor substrate, which generally has the formation of an insulation film of SiO2 or Si3N4 on at least part of its surface will be charged accidentally when a charged-particle beam, e.g., an electron beam, is projected to the surface.
Conventional techniques dealing with the above-mentioned matter are described in Japanese Laid Open Publication No.S63(1988)-133640 (prior art 1), No.H1(1989)-119668 (prior art 2), No.H1(1989)-243449 (prior art 3), and No.H4(1992)-152519 (prior art 4)
The prior art 1 is intended for electron beam testing by projecting an electron beam to a semiconductor sample and detecting secondary electrons released from the sample thereby to evaluate the potential at each position of the sample. It describes the prevention of charging by dispersing charges, which are accumulated on the sample surface due to the projection of electron beam, based on the photoconduction effect which is induced by the irradiation of light from a laser source or light source, e.g., a tungsten lamp, to the sample surface.
The prior art 2 is intended for an ion implant apparatus having an ion source, ion analyzer and accelerator. It describes the dissolution of impropriety (breakdown of a thin SiO2 insulation film) caused by charge-up due to ion implantation based on the irradiation of the entire Si wafer surface coated with a SiO2 insulation film with a ultraviolet (will be termed xe2x80x9cUVxe2x80x9d hereinafter) light from a low-voltage mercury lamp or ArF laser (with a wavelength of 193 nm) thereby to energize carriers in SiO2, which is immediately followed by the lead-out of positive charges, which have been created by ion implantation, through a disc or clamp. Namely, the prior art 2 uses a UV light which passes through SiO2 for putting energy on the border surface between Si and SiO2.
The prior art 3 is intended for the sputtering process of a wiring modification point on a Si substrate, which has the formation of an insulation film on the surface, of a semiconductor device based on the projection of ion beam, and for the formation of W wires through holes, which have been formed by the sputtering process, based on the projection of ion beam in a gaseous atmosphere of W(CO)6 or the like. It describes the neutralization of the insulation film surface by using electrons energized by the irradiation of UV light.
The prior art 4 is intended for the fabrication of a semiconductor device. It describes the process for charge-up of charged particles based on the irradiation of the semiconductor substrate surface with a UV light with a wavelength of 398-141 nm for a SiO2 insulation film or 617.3-246.9 nm for a Si3N4 insulation film following a process, by which charges are accumulated in the semiconductor substrate, among dry etching, ashing, plasma CVD, electron beam exposure, ion implantation, pure water washing, and wafer SEM.
However, none of these prior arts 1 through 4 consider the prevention of the drift of charged-particle signal or the deterioration of contrast at the detection of charged-particles, e.g., secondary electrons or reflected electrons, from the sample of semiconductor substrate or the like caused by charges emerging on the insulator due to the projection of charged-particle beam to the sample surface, and none of the prior arts consider the avoidance of the influence of photoelectrons emerging at the irradiation of the insulator with a UV light.
Another problem which is left unconsidered in these prior arts 1 through 4 is the creation of burnt insulation substance due to the projection of a charged-particle beam, e.g., an electron beam, to the aperture, for example, within the barrel of a charged-particle beam apparatus, e.g., an electron beam apparatus, and the occurrence of charge-up due to the projection of charged-particle beam to the insulation substance, which results in a fluctuated beam position or spot diameter of the charged-particle beam, e.g., an electron beam, emitted from the barrel.
An object of the present invention is to provide a method and apparatus for inspecting or measuring a sample based on charged-particle beam imaging, with the foregoing prior art problems being overcome.
In order to achieve the above objective, the present invention resides in a method of inspecting or measuring a sample based on charged-particle beam imaging, the method comprising an inspecting or measuring step of projecting, while scanning, a converged charged-particle beam to a sample which has the formation of an insulation film on at least part of the surface thereof, detecting charged particles which are released from the sample due to the projection of scanning charged-particle beam, thereby producing a charged-particle image, and processing the produced charged-particle image, thereby performing the inspection or measurement of the sample, and a conduction rendering step of irradiating the sample with a UV light to make the insulation film conductive, thereby causing charges to flow out of the sample.
The present invention also resides in a method of inspecting or measuring a sample based on charged-particle beam imaging, the method projecting, while scanning, a converged charged-particle beam to a sample which has the formation of an insulation film on at least part of the surface thereof, detecting charged particles which are released from the sample due to the projection of scanning charged-particle beam, thereby producing a charged-particle image, processing the produced charged-particle image, thereby performing the inspection or measurement of the sample, and irradiating the sample with a UV light to energize electrons in the insulation film on the sample surface, thereby making the insulation film conductive.
The present invention also resides in an apparatus for inspecting or measuring a sample based on charged-particle beam imaging, the apparatus comprising a stage for placing a sample which has an insulation film, a charged-particle source, a charged-particle focusing system which converges the charged-particle beam emitted by the charged-particle source, a scanning means which deflects the charged-particle beam converged by the charged-particle beam focusing system to project, while scanning, the charged-particle beam to the sample placed on the stage, an imaging means which detects charged particles released from the sample due to the projection of charged-particle beam by the scanning means, thereby producing a charged-particle image, an image processing means which processes the charged-particle image produced by the imaging means, thereby performing the inspection or measurement of the sample, and a UV light irradiation means which irradiates the sample with a UV light to energize electrons in the insulation film, thereby making the insulation film conductive.
The present invention also resides in a charged-particle beam apparatus which comprises a stage for placing a sample which has an insulation film, a charged-particle source, a charged-particle focusing system which converges the charged-particle beam emitted by the charged-particle source, a scanning means which deflects the charged-particle beam converged by the charged-particle beam focusing system to project, while scanning, the charged-particle beam to the sample placed on the stage, a detector means which detects charged particles released from the sample due to the projection of charged-particle beam by the scanning means, an imaging means which produces a charged-particle image of the sample based on the signal of charged particles detected by the detector means, a barrel means which accommodates the stage, charged-particle source, charged-particle focusing system and detector means, and a UV light projection means which projects a UV light to the interior of the barrel means.
The inventive method and apparatus arranged as described above are designed to irradiate a sample with a UV light thereby to prevent the insulation film on the sample from being charged, so that an accurate and high-contrast charged-particle image which is rid of a noise component created by the UV light irradiation can be produced stably, thereby accomplishing the inspection of small extraneous substances and defects on fine patterns and the dimensional measurement of fine patterns at a high sensitivity and high reliability.
The inventive method and apparatus are designed to irradiate the sample of semiconductor substrate or the like with a UV light thereby to prevent the insulation film of SiO2, Si3N4, etc. on the sample from being charged, while minimizing the adverse effect of UV light irradiation on underlying elements beneath the insulation film so that an accurate and high-contrast charged-particle image which is rid of a noise component created by the UV light irradiation can be produced stably, thereby accomplishing the inspection of small extraneous substances and defects on fine patterns and the dimensional measurement of fine patterns at a high sensitivity and high reliability.
The inventive method and apparatus are capable of preventing the fluctuation of the beam position, focal position and astigmatism of the charged-particle beam, e.g., an electron beam, caused by charge-up of the interior of the barrel of a charged-particle beam apparatus, e.g., an electron beam apparatus, thereby accomplishing the inspection of small extraneous substances and defects on fine patterns and the dimensional measurement of fine patterns at a high sensitivity and high reliability.
The inventive method and apparatus are capable of improving the efficiency of charged-particle beam emission from the charged-particle source, e.g., an electron gun, in the barrel of a charged-particle beam apparatus, e.g., an electron beam apparatus, thereby accomplishing a high-efficiency charged-particle beam apparatus.
These and other objects, features and advantages of the present invention will be apparent from the following more particular description of the preferred embodiments of the invention, as illustrated in the accompanying drawings.